1. Field of the Invention
This invention relates to a copper-based alloy and a method for producing the same. More particularly, it is concerned with a copper-based alloy for use as component parts for electrical apparatuses and appliances, in particular, as a semiconductor lead frame.
2. Description of the Prior Art
The material for the semiconductor lead frame is required to have various properties such as high electrical conductivity, high mechanical strength, repetitive being capability, soldering capability, plating capability, heat-resistant property, low thermal expansion coefficient, and so forth.
Heretofore, an "Fe-Ni series 42 alloy" with high mechanical strength and less thermal expansion has been principally used as the material for the semiconductor lead frame. In recent years, however, this conventional trend has changed remarkably due to preference on the part of users of high output, multi-function, high productivity, and a low cost in the semiconductor device, as the result of which use of copper-based alloy which is inexpensive and possesses high electrical conductivity has become increased.
Ideal yardsticks for the characteristics of the material for the semiconductor lead frame in respect to a tensile strength, elongation, and electrical conductivity are, in general, said to be 50 kg/mm.sup.2 and above for the tensile strength, 10% and above for the elongation, and 50% IACS and above for the electrical conductivity. However, nothing in the existing materials which have so far been known perfectly satisfies these standard values, and there have so far been put to practical use only the Fe-Ni series 42 alloy and phosphor bronze with predominant mechanical strength and repetitive bending property, and various copper-based alloys composed of copper as the principal constituent and a very small amount of alloying elements added to it, with emphasis being placed on the electrical conductivity and market price of the article.
However, these conventional 42 alloy and phosphor bronze have low electrical conductivity, and are inevitably expensive due to high cost of the constituent elements. On the other hand, the copper-based alloys composed of copper as the principal constituent, to which a very small quantity of alloying elements is added, are not satisfactory in their tensile strength, repetitive bending property, heat-resistant property, and so on.